JPS6117222B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a power system stabilizing device used when a synchronous machine is connected to a power system and operated. A synchronous generator usually has an automatic voltage regulator (hereinafter abbreviated as AVR) that automatically adjusts its output voltage.
However, in recent years, the distance between power plants and loads has increased, the capacity of generators and transformers has increased, and the economic design associated with this has caused the power system to become unstable. Impedance tends to increase, and it is becoming difficult to maintain stable operating conditions with the AVR alone during power fluctuations such as power system failures. Recently, as a method to deal with this increase in power system impedance, a method has been developed that detects changes in the generator's frequency or rotational speed (hereinafter referred to as changes in frequency, etc.) Δω and supplies it to the AVR as an auxiliary signal. has been adopted. Devices that do this are generally power system stabilization devices (hereinafter referred to as
(abbreviated as PSS). If we consider the case where a generator receives mechanical input PM from a prime mover (such as a water wheel or turbine), converts it into electrical output PG, and transmits it to the power grid, under normal conditions the condition PM = PG is satisfied. If this is true, the generator is operated at a certain phase angle δ with respect to the receiving side of the power system (which can be regarded as an infinite bus) without being accelerated or decelerated. However, if a short circuit or ground fault occurs in the power system, the transfer impedance between the generator and the receiving side of the power system increases, and the output PG of the generator decreases compared to before the accident. On the other hand, mechanical input PM is
Since it does not change immediately, an unbalanced state occurs where PM>PG, and the generator is accelerated and the internal phase angle δ relative to the power receiving side of the power system begins to open. If the internal phase angle δ exceeds a certain value, even if the fault in the power grid is removed, the generator will no longer be able to maintain connection with the power grid, resulting in an out-of-step state. At this time,
The PSS detects that the frequency of the generator has increased due to a system fault, and supplies a signal to the AVR to increase the internal induced voltage of the generator, increasing the generator output PG and increasing the mechanical input PM. In other words, the acceleration energy is reduced to suppress the opening of the internal phase angle δ. As described above, PSS detects that the generator output PG has suddenly decreased and the generator has accelerated, and increases the excitation of the generator to increase the internal induced voltage. By the way, the reason for the sudden decrease in generator output PG is
In addition to the various types of failures in power systems as described above, there are also load interruptions, load dropouts, and the like. Therefore, in this case as well, the PSS operates to supply a signal to the AVR and increase the generator voltage. However, there is no need to increase the generator voltage in the case of a load failure, etc., and if the PSS is activated instead, the voltage will rise abnormally, which will be inconvenient for power equipment such as the generator. As a method for solving such inconveniences, the configuration shown in FIG. 1 has conventionally been adopted. In FIG. 1, reference numeral 1 indicates a generator, and the generated output of the generator 1 is supplied to an electric power system 8 via a generator shield and a disconnector 7. As shown in FIG. The power system 8 is connected to a load 10 via a load switch 9 . 3
is the automatic voltage regulator AVR mentioned above, and this AVR
3 is supplied with a magnetizing signal from the above-mentioned power system stabilizing device PSS5 via a contact 4, and a generator output via an instrument transformer 2, respectively. The AVR 3 increases the field current flowing through the field winding 6 of the generator 1 using the magnetization signal. Now, when the generator disconnector 7 is opened due to a load disconnection, etc., the output of the generator 1 is
It suddenly decreases, and PSS5 tries to send a magnetization signal to AVR3. However, since the contact 4 is an auxiliary contact of the generator switch 7 and is open, the magnetization signal is not supplied to the AVR 3. Therefore, the output voltage of the generator 1 will not rise abnormally. Next, if a failure such as a ground fault occurs in the power system 8 and the generator output suddenly decreases, the generator
remains closed and the contact 4 is also closed, so the magnetizing signal of the PSS 5 is supplied to the AVR 3 and increases the induced voltage and stability of the generator 1. However, in the above configuration, since the signal from the PSS 5 is interlocked by the auxiliary contact 4 of the generator/disconnector 7, the load/disconnector/disconnector is not the generator/disconnector 7; Interlocking becomes impossible when the power system 8 becomes complicated, such as a load disconnection, a load disconnection 9, or a combination thereof. As a result, when the power system is complex, there is a drawback that the signal from the PSS 5 may be disconnected even though it is necessary, or may not be disconnected even though it is unnecessary. This invention was made to eliminate the above-mentioned drawbacks of the conventional technology, and by providing a PSS control circuit, it eliminates the need for an auxiliary contact for the circuit breaker.
It is an object of the present invention to provide a power system stabilizing device whose operation is performed appropriately. Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5. FIGS. 2 and 3 show a first embodiment of the invention. In Figure 2, symbols 1-3, 5-1
Each part of 0 has the same structure as the corresponding part of FIG. 1 above. Therefore, the explanation of that part will be omitted. In FIG. 2, 11a is the control relay 11 in FIG.
The PSS 5 is designed to supply an auxiliary signal Δω to the AVR 3 via this contact 11a. 13 is a current detection relay, which detects the output current of the generator 1 by the instrument current transformer 12;
It operates when the value is greater than or equal to a predetermined value. In FIG. 3, reference numeral 11 denotes a control relay having the contact 11a, to which the contact 13a of the current detection relay 13 and the pressure switch 14 are connected in series. The pressure switch 14 detects the steam pressure proportional to the load of the turbine driving the generator 1, and normally the steam pressure at the inlet of the low-pressure turbine is used as the detected pressure. The pressure switch 14 is closed when the load exceeds a certain value _P1 . When there are no accidents in the power system and the generator is operating normally, the set value I ₁ of the current relay 13 and the set value P ₁ of the pressure switch 14 are proportional to the generator output; In terms of output, I ₁ <
There is a relationship of P ₁ . Therefore, the relationship with the operating status of the generator is tabulated as follows.

[Table] As shown above, it can be seen that in the normal state, the contact 11a is closed only when the generator output is P1 _or more. As a result of power system analysis, this means that if the generator output is less than P ₁ , even if an accident occurs in the power system,
Does not require PSS. That is, set the value of P ₁ as such. Next, if an accident such as a single line ground fault occurs in the power system, or a load disconnection occurs, the table below shows the situation.

[Table] As described above, the contact 11a maintains the closed state and supplies the auxiliary signal Δω to the AVR 3 only when an accident occurs and the generator output immediately before the accident is _P1 or more. In the table above, the column marked * for contact 14 is closed because the generator output decreases to less than P ₁ at the same time as the trouble occurs, but as mentioned above, contact 14 is closed.
4 is a steam pressure switch, so it does not drop suddenly and maintains the state immediately before the trouble occurs. In addition, the reason why the contact 13a is closed in the event of an accident and open in the event of a load interruption is because the reactive current increases in the event of an accident, so a current exceeding the set value of the current detection relay 13 flows. This is because sometimes the electric current suddenly decreases along with the electric power, and becomes less than the set value of the current relay 13. Further, FIGS. 4 and 5 show a second embodiment of the present invention. This embodiment is basically the same as the one shown in FIG. 2, but the only difference from FIG. 2 is that a power detection relay 14 is provided. This power detection relay 14 receives the generator voltage supplied via the instrument transformer 2 and the output current supplied from the current transformer 12 as input, detects the generator power, and sets the power value to the set value P. ₁ or more, it operates and closes its contact 14a shown in FIG.
In the contact circuit shown in FIG. 5, a time limit relay 15 is connected to the contact 14a. On the other hand, these contacts 14a
A series circuit of the same control relay 11 and contact 13a as shown in FIG. 3 is connected in parallel to the series circuit of the time limit relay 15. The contact 13a is connected to an a contact 15a for instantaneous operation and time-limited return of the time-limited relay 15. Now, when there is no accident in the power system and the generator is operating normally, the setting value of the current relay 13 is proportional to the generator output, and there is a relationship of I ₁ < P ₁ in terms of output. The relationship with the operating status of the generator is tabulated as follows.

[Table] As described above, in the normal state, the contact 11a is closed and the auxiliary signal Δω is supplied to the AVR 3 only when the generator output is P ₁ or more. _P1
If it is less than 1, PSS 5 is not required, which is the same as in the first embodiment. Next, if an accident such as a single line ground fault occurs in the power system, or a load disconnection occurs, the table below shows the situation.

[Table] As described above, the contact 11a is closed only at the time of an accident and only when the generator output immediately before the accident is P1 _or more. In the table, the * marked part of contact 15a is closed because the generator output decreases to less than P ₁ as soon as a trouble occurs, but contact 15a is closed as long as the time limit setting of the time limit relay is still within the time limit. This is because the state is maintained. Further, the contact 13a is closed in the event of an accident and opened in the event of a load break for the same reason as shown in FIG. As described above, according to the present invention, the auxiliary signal of the power system stabilization device is reliably activated only in the event of an accident when the generator output immediately before a trouble occurs is above a certain set value.
The signal is transmitted to the AVR, and the signal from the power system stabilizing device is cut off when the load is interrupted. This prevents abnormal voltage rises, etc. that occur in the past. Optimal operation becomes possible. In the above embodiment, the AVR signal flows directly to the field winding 6 of the generator, but it goes without saying that an exciter may be interposed in between.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional power system stabilizing device, FIG. 2 is a block diagram showing the configuration of a power system stabilizing device according to a first embodiment of the present invention, and FIG. The contact circuit diagram, Figure 4, is
FIG. 5, a block diagram of a second embodiment of the present invention, is a contact circuit diagram thereof. 1... Generator, 2... Instrument transformer, 3... Automatic voltage regulator (AVR), 5... Power system stabilizer (PSS), 6... Field winding, 7... Generator switch and disconnector, 8
...Power system, 10...Load, 11...Control relay, 1
2... Current transformer, 13... Current detection relay, 14... Pressure switch, 15... Time limit relay.

Claims (1)

[Claims] 1. An automatic voltage regulator that automatically adjusts the output voltage of the synchronous generator, and a change in the frequency or rotational speed of the synchronous generator that is detected and transmitted to the automatic voltage regulator. A power system stabilizing device that supplies an auxiliary signal, a current detection relay that detects the output current of the synchronous generator and operates when the detected current exceeds a predetermined value, and a current detection relay that detects the output current of the synchronous generator and operates the synchronous generator from the steam pressure of the turbine. The pressure switch detects the output of the generator, and when the generator output during normal conditions exceeds the set value, or when the generator output immediately before the accident exceeds the set value, the current detection relay and the pressure switch Operated by the operation of a switch, the contact provided in the connection path between the power system stabilizing device and the automatic voltage regulator is closed, and an auxiliary signal is supplied from the power system stabilizing device to the automatic voltage regulator. A power system stabilization device consisting of a control relay. 2. A synchronous generator, an automatic voltage regulator that automatically adjusts the output voltage of the synchronous generator, and a system that detects changes in the frequency or rotational speed of the synchronous generator and transmits them to the automatic voltage regulator. A power system stabilizing device to be supplied as an auxiliary signal; a current detection relay that detects the output current of the synchronous generator and operates when the detected current exceeds a predetermined value; A power detection relay that detects, a time limit relay that maintains the operating state of this power detection relay for a certain period of time, and a generator output that is set when the normal generator output exceeds a set value, or when the generator output immediately before an accident occurs. When the current detection relay and the time limit relay operate to close the contact provided in the connection path between the power system stabilization device and the automatic voltage regulator, the power system is stabilized. A power system stabilizing device comprising a control relay that supplies an auxiliary signal from the automatic voltage regulator to the automatic voltage regulator.